The present invention relates to ceramic fiber modules for insulating the interior of a high temperature furnace. In particular, this invention describes a module and method of using the same in which the module comprises a ceramic fiber shell-like form, a plurality of ceramic fiber blankets situated within the shell-like form and means for joining the shell and contents to a furnace housing which generally is of steel.
For many years heat treating furnaces, ceramic kilns, brick kilns, and the like, were lined with dense fireclay brick. Later insulating firebrick replaced the dense fireclay brick because of its lighter weight and better insulating properties. Recently ceramic fiber material made of alumina-silica fibers made into blankets has replaced the insulating firebrick as lining for such furnaces and kilns. The latest advances in this art is the use of module units in which the ceramic fiber blankets are positioned on end, or edge grain, and retained in a blanket which is designed to be attached to the steel frame defining the furnace or kiln.
The rolls of ceramic fibers typically are impaled upon metal studs welded to the furnace walls. This arrangement has several drawbacks, namely that the temperature limit of the construction is dependent on the temperature that the metal studs can stand. Another drawback is that the ceramic fiber blankets are easily damaged, torn and also tend to shrink lengthwise with high temperature use so that gaps are formed between the ends of the blankets.
For economic reasons, it is undesirable to replace a large layered blanket module, which has only a relatively small damaged area. However, unless the blanket is replaced, the damaged area will grow in size.
In order to facilitate replacement of damaged insulation, numerous modular insulation articles have been developed.
The modules eliminate much of the temperature limitation, but there is a possibility that heat can flow between the modules and between the strips of ceramic fibers mounted in the modules. In all of these modules, the blankets are perpendicular to the furnace wall and therefore the thermal conductivity and refractoriness of the module is uniform from hot face to cold face.
Typical of such construction are the Sauder U.S. Pat. Nos. 3,819,468 and 3,993,237. These devices still require a welded stud on the furnace frame and time consuming application. Other patents exemplifying this type construction including Balaz et al U.S. Pat. No. 3,832,815 in which a series of strips of ceramic fibers are clamped together into a module for installation on furnace walls. Still other such devices are shown in Byrd U.S. Pat. Nos. 4,001,996 and 4,123,886.
As mentioned, in all of the foregoing listed patents the fibers in the blanket lie in planes generally perpendicular to the furnace wall. In addition many of these devices require a welded stud on the furnace wall and several of the patents disclose impaling or spearing the ceramic blanket on a pin or stud mounted on the furnace wall with a washter mounted on the end of the stud to hold the blanket in place. These arrangements tend to allow the blanket to sag or tear away from the furnace wall and the stud serves as a conduit for heat from the blanket to the furnace wall.
Accordingly it is a principle object of the present invention to provide a ceramic fiber module in which layers of ceramic fiber blankets are all positioned in a plane parallel to the surface of the furnace wall inside a shell-like form. It is a further object to provide a simple effective means for attaching such ceramic fiber modules to a furnace wall in an efficient and safe manner. It is a further object to provide a method for fastening such ceramic fiber modules to a furnace wall without providing a direct conduit for heat to pass from the furnace to the outside shell.
Still another object is to provide a module of ceramic fiber blankets in which the end of the module closest to the heat of the furnace has a high temperature resistant fiber blanket positioned therein. Closer to the furnace wall are high heat transfer resistance materials.
A still further object is to provide a "T" shaped anchor which is fastened to a furnace frame and retains modules in side-by-side arrangement on the wall while the anchor is protected from direct furnace heat.
These and other objects and advantages will become apparent hereinafter.